"This award is in recognition of the mayor's visionary and planet-changing leadership that has created the amazing legacy of a green city," the council said.

During Daley's 21-year tenure as mayor, Chicago has planted more than 600,000 trees, constructed more than 85 miles of landscaped medians and built more than 7 million square feet of planted roofs — more than any other city in the U.S., city officials have said.